Monsoon Storms in Tucson

When we first pulled into Tucson in June 2014, it was at the beginning of monsoon season. I’ve always been a weather geek so I was interested in learning more about what monsoon season meant. 

Basically, monsoon season begins when there is a shift in wind direction. Typically, Arizona gets a west to east flow of weather, but during monsoon season, pattern shifts, most often due high pressure sitting overtop of the Four Corners region. This allows the flow of air to come from the Gulfs of Mexico and/or California (a southeasterly flow), bringing moisture. I realize it is a bit more complex than that explanation, but that gives you an idea of what makes moisture flow into southern Arizona. Below is a good visual of this weather pattern, and you can learn more in Jeff Beamish’s Monsoon Classroom blog articles.


Moving from Harrisburg, I admit I was quite skeptical of the dangers of monsoon seasons. I kept thinking, “How bad can it really be?”

I quickly discovered that it can be quite bad. Here’s why (in my unscientific terms):

  • The desert ground has been baked by the sun for centuries – making it practically non-porous. So any amount of rainfall Tucson gets, even just 0.25 inches, just sits on top of the ground.
  • It rains most over the mountains – Tucson, Catalina and Rincon – so even though town may only receive a little rain, flash flooding occurs from water flowing out of the mountains into the bowl of Tucson.
  • There are desert washes everywhere, and most of the year, they are dry. But after a rainstorm, they flow for a few hours and are dangerous to cross.
  • Some of Tucson’s roads were specifically engineered to carry water to washes and rivers during periods of heavy rain. This means flooding to downtown roads.

Below is a video from water flowing across a wash on the northwest side of Tucson. Silverbell is a road we travel often.

Sky Watch

The other aspect about Monsoon season is that you have to be a weather watcher, especially if you are traveling from one area of town to another. Just like I used to watch for winter weather – snow, sleet and freezing rain – on the East Coast, I need to watch the clouds here in Tucson.

While there aren’t any runs to the grocery store for bread, milk and eggs like there are before a winter storm back east, there is thoughtful consideration about whether or not you are going to venture out.

A storm is brewing over the Catalina Mountains.
A storm is brewing over the Catalina Mountains.

Earlier this summer, I was running errands in an area five miles from home. The sky turned dark, and rather than trying to fit in that last stop for dog food, I decided to head home. I am glad I did.

When I started my journey back towards home, it was 104F. The rain came down hard and fast, and the “dippy roads” leading to my house quickly started filling up with water. I turned into my development to see a river running down the hill. I made it home safely, and the temperature had dropped to 73F – a 31 degree difference in a matter of 15 minutes!

While the “Do Not Enter When Flooded” signs still make me giggle almost as much as “Bridge Freezes Before Road” signs do out here, I’ve gained a complete respect for the power of monsoon season in Tucson. Stay safe!

The aftermath of a heavy rainstorm - inches of dirt across the road.
The aftermath of a heavy rainstorm – inches of dirt across a road leading to our home.


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